JPH08980B2 - Plasma CVD method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD method (plasma CVD method) in which a raw material gas introduced between a cathode electrode and a ground electrode in a film forming chamber is turned into plasma and the substrate is exposed to the plasma to form a thin film on the substrate. Chemical vapor deposition method) and apparatus.

[0002]

2. Description of the Related Art Plasma CVD methods and devices are widely used for forming various thin film devices such as amorphous silicon (a-Si) solar cells and liquid crystal display devices. As a typical example of an apparatus for carrying out the plasma CVD method, a capacitively coupled plasma CVD apparatus shown in FIG.

In this plasma CVD apparatus, a cathode electrode 2 and a ground electrode 3 are arranged opposite to each other in a film forming chamber 1, and a high frequency power source (RF power source 13.56 MHz) 40 is connected to the cathode electrode 2 through a matching box 4a. A substrate 9 is arranged on the ground electrode 3, and the substrate 5 is controlled by the heater 5 at the film forming temperature. Further, the film forming chamber 1 is connected to an exhaust system 6 for obtaining a predetermined degree of vacuum and a source gas supply device 7 for supplying a source gas.

According to this apparatus, the substrate 9 on the ground electrode 3 is
Is controlled by the heater 5 to the film forming temperature, and while the inside of the film forming chamber 1 is maintained at a predetermined film forming vacuum degree by the exhaust system 6, the source gas is introduced into the film forming chamber from the source gas supply device 7. As shown in FIG. 5B, high frequency power is continuously applied to the cathode electrode 2 from the power source 40 at a constant output to convert the raw material gas into plasma, and the surface of the substrate 9 is exposed to the plasma. As a result, a desired thin film is deposited and formed on the surface.

[0005]

However, the above-mentioned conventional method and apparatus have the following problems. When the raw material gas is turned into plasma, the state of the plasma, in particular, the generation of various radicals due to turning into plasma cannot be controlled, and therefore the generation of radical species unnecessary for film formation cannot be suppressed, which is considered to be due to such unnecessary radicals. The generation of dust and particles cannot be suppressed, which hinders the formation of a good quality film. When the high frequency power source output is increased in order to carry out high-speed film formation, the unnecessary radical species also increase accordingly, so that it is difficult to form a high-quality film at high speed. Since it is difficult to increase the high-frequency power output because it suppresses the generation of unwanted radicals, the plasma density is reduced accordingly, while the width of the sheath region between both electrodes is increased, and high-speed ions accelerated in this sheath region form the film formed. And the film is easily damaged. As one attempt , simply turn the high frequency power on and off.
When pulsed to apply return Ri, and the like from a portion of the electrode discharge starts, there is a tendency that plasma becomes unstable. Therefore, the present invention is a plasma CVD method and apparatus for converting a source gas introduced between a cathode electrode and a ground electrode in a film forming chamber into plasma, and exposing the substrate to the plasma to form a thin film on the substrate. To turn the plasma into
Control radical generation to generate radicals required for film formation
While not interfere with, it is possible to suppress the generation of unnecessary the radical Le to the deposition, whereby the dust, while suppressing the generation of particles can be stably formed a thin film of high quality at high speed plasma CV
It is an object to provide a D method and a device.

[0006]

The inventors of the present invention have conducted extensive research to solve the above-mentioned problems. As a result, the radicals present in plasma contribute to the formation of a good quality film and cause the generation of dust and the like. it is composed of one and is, then, generation of various radicals present in the plasma, electron energy,
Since it largely depends on the density, by controlling this electron energy and density, it is possible to selectively increase the quality radical species necessary for film formation, while generating unwanted malicious radicals that are thought to cause dust and particles. In addition, a good quality radical has a relatively short energy application time for its generation and a long life, whereas a bad radical has a long energy application time for its generation and a long life. Have short characteristics,
Therefore, the electron energy and density are controlled, and as a control method therefor, an energy source for plasma conversion into a source gas is used.
It is only necessary to introduce the electric energy in the form of a pulse that repeatedly turns on and off . Moreover, as shown in FIG.
In addition to the pulsed application in which the on / off of the microwave is repeated, by introducing the pulsed application in which the on / off of the microwave is repeated, it is possible to increase the density and stability of high-quality radicals that cannot be obtained only by the pulsed application of high frequency power. The inventors have found that they can be realized and completed the present invention.

FIG. 4 shows a pulsed application in which the high frequency power is repeatedly turned on and off in the case of the conventional high frequency power application (FIG. A).
In case (Fig. B), both high frequency power and microwave are turned on.
・ Relative ratio of electron energy and density to the output state when applying in the form of a pulse that repeatedly turns off (Fig. C), each output
The relative ratio of the good quality radical density to the bad radical density in the state is illustrated. As can be seen from these figures , pulse marks for both high frequency power and microwave
In the case of addition, the relative ratio of electron energy / density and the relative ratio of good quality radical density are greatly increased as compared with the other cases.

That is, according to the present invention, the source gas introduced between the cathode electrode and the ground electrode in the film forming chamber is turned into plasma,
In the plasma CVD method in which a substrate is exposed to this plasma to form a thin film on the substrate , plasma conversion of the source gas is performed.
The high frequency power to the cathode electrode is turned on and off repeatedly.
Applying a pulsed pulse back and applying microwaves to the deposition chamber.
The pulsed voltage is repeatedly turned on and off.
A plasma CVD method characterized in that the application of a microwave is performed in synchronism with the application of the high-frequency power , and a source gas introduced between a cathode electrode and a ground electrode in a film forming chamber is converted into a plasma, and the plasma is generated. In a plasma CVD apparatus that exposes a substrate to a substrate and forms a thin film on the substrate, high-frequency power is turned on to the cathode electrode to turn the source gas into plasma.
A means for repeatedly applying OFF in a pulse shape, a means for repeatedly applying ON / OFF to the film forming chamber in a pulse shape, and a microwave for applying the microwave.
The present invention provides a plasma CVD apparatus characterized in that it is provided with means for synchronizing with the application of force .

This plasma CVD method and apparatus according to the present invention
For example, each ON time of high frequency power (high frequency
Wave pulse width) t1 is 1 × 10 ⁻³ seconds ≦ t1 ≦ 10 × 10 ⁻³
Second, each off time t2 of high frequency power is 1 × 10 ⁻³ seconds ≦ t2
≤10 × 10 ^-3 seconds, each microwave on-time (micro
Wave on-pulse width) t3 is 2 × 10 ⁻³ seconds ≦ t3 ≦ 15 × 1
0 ^-3 seconds, each microwave off time t4 is 1 x 10 ^-3 seconds ≤
It can be considered that t4 ≦ 10 × 10 ⁻³ seconds.

Application of the microwave and high frequency power
At the timing of the start, the microwave may be a applied by precede the high frequency power, in that case, the high-frequency power application start delay time t5 to 1 × 10 ^-3 seconds or more of
On the other hand, it may be set to 5 × 10 ⁻³ seconds or less. high frequency
It is conceivable that the power output is set to the optimum output in consideration of the electrode area and the microwave output is set to about 50 to 500W.

[0011]

According to the method and apparatus of the present invention, high-frequency power is applied to the cathode electrode in a pulsed manner that is repeatedly turned on and off.
Microwave is repeatedly turned on and off in the film formation chamber
The pulse is applied and the microwave is applied at high frequency.
By being applied in synchronization with the application of wave power, the cathode electrode
The source gas between the ground electrode and the ground electrode is turned into plasma. This and
As shown in FIG. 4C, a good quality
Cull is selectively generated, increased, increased in density, and stabilized.
On the other hand, in the state where the generation of radicals unnecessary for film formation is suppressed,
The source gas is turned into plasma, and the substrate is exposed to this plasma.
By doing so, a good quality thin film can be formed on the substrate quickly and stably.
Is made. In addition, the start of microwave and high frequency power application
As for timing, microwave is less than high frequency power
When starting application prior to
Zuma state can be obtained quickly and radical control becomes easier.
Therefore, a high quality film can be formed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1, FIG. 2 and FIG. 3 are schematic diagrams showing the first, second and third examples of the plasma CVD apparatus for carrying out the method of the present invention. Compared with the conventional device shown in FIG. 5, the power applying means for the cathode electrode 2 is different and a microwave applying introducing means for the film forming chamber 1 is newly added to each of the devices, but the other parts are different. It has substantially the same configuration as the conventional device. The same parts as those in the conventional apparatus are designated by the same reference numerals.

In the plasma CVD apparatus of FIG. 1, high frequency power is applied to the cathode electrode 2 by repeatedly turning on and off a pulse.
High frequency pulse generator 4 is applied to Jo, and the film forming chamber 1 comprises a microwave pulse generator 8 for applying introducing microwaves caused by repeated on-off pulses. The high frequency pulse generator 4 repeatedly turns on and off the high frequency.
It includes a high frequency pulse signal generator 41 for generating a pulse signal to be returned , a power amplifier 42 for making the pulse signal from the generator a high output, and a high frequency matching box 43.

The microwave pulse generator 8 includes a microwave pulse signal generator 81 for generating a pulse signal for microwaves, a microwave transmission source 82, and an isolator 83 for preventing a reaction of the microwave toward the source. A matching device 84 for matching adjustment and a waveguide 85 for guiding microwaves to the film forming chamber 1 are included. The waveguide 85 is provided with a ceramic member 851.

Between the high frequency pulse signal generator 41 and the microwave pulse signal generator 81, there is provided a phase synchronizing circuit 80 for synchronizing the high frequency pulse and the microwave pulse. The plasma CVD apparatus of FIG. 2 has the same configuration as the apparatus of FIG. 1 except that a multi-pin coaxial antenna type is adopted as a method of introducing microwaves into the film forming chamber 1.
That is, in this device, microwaves are guided by the waveguide 85 in the device of FIG.
And is introduced from each cable through antennas 87 provided at several positions in the film forming chamber, and other configurations are the same as those of the apparatus of FIG. Since the cable 86 and the antenna 87 are arranged in parallel with the electrodes, only one each is shown in FIG.

The plasma CVD apparatus of FIG. 3 has the same structure as the apparatus of FIG. 1 except that a plasma generation tube type is adopted as a method for introducing microwaves into the film forming chamber 1. That is, in this apparatus, the raw material gas in the quartz reaction tube 88 is adjusted by the microwave reflection plate 881 into a high density plasma by the microwave guided from the waveguide 85, and is introduced into the film forming chamber 1. To do. A plurality of reaction tubes may be provided. The raw material gas is supplied from the gas supply device 7 to the valve 89.
Feed through.

According to each of the above devices, the method of the present invention is carried out as follows. In any of the above-mentioned devices, both introduction of a microwave pulse to the film forming chamber 1 and application of a high frequency pulse to the cathode electrode 2 are performed at the same time by synchronizing both pulses, and the microwave and the high frequency are applied. Of pulse
Regarding the initial application start timing, the microwave is performed before the high frequency.

The high frequency on-time (high frequency pulse width) t1 is
1 × 10 ⁻³ sec ≦ t1 ≦ 10 × 10 ⁻³ sec , high frequency off time t2 is 1 × 10 ⁻³ sec ≦ t2 ≦ 10 × 10 ⁻³ sec , microwave on time (microwave pulse width) t3 is 2 × 10 ^-3 seconds
≦ t3 ≦ 15 × 10 ⁻³ seconds , microwave off time t4 is 1
× 10 ⁻³ seconds ≦ t4 ≦ 10 × 10 ⁻³ seconds . Further, the application delay time t5 of the high frequency with respect to the microwave is set to 1 × 10 ⁻³
Not less than 2 seconds and not more than 5 × 10 ⁻³ seconds .

The high frequency output is set to the optimum output in consideration of the electrode area, and the microwave output is set to about 50 to 500W. Thus, the high frequency power is turned on and off to the cathode electrode 2 repeatedly.
It is applied in a pulse shape by returning, and the microwave is applied to the film forming chamber 1 in a pulse shape by repeatedly turning on and off, and
The application is synchronized with the application of high frequency power except when the application is started.
By adding the source gas between the cathode electrode 2 and the ground electrode 3 to plasma under a predetermined film formation vacuum degree, the substrate 9 on which the temperature is controlled on the ground electrode 3 is exposed to this plasma. A desired thin film is formed on 9.

In this film formation, for example, 2 × 10 ^-3 to 1 is used in order to remove unnecessary radicals whose time density increases slowly.
After maintaining plasma generation for about 0 × 10 ^-3 seconds , 1 × 10
^{Since the} pulse operation is performed so as to provide an off time of about ⁻³ to 10 × 10 ⁻³ seconds , radicals necessary for high-quality film formation have a long life and hardly decrease, and selectively increase at this time. However, the film formation rate does not decrease, and on the other hand, the generation of radical species unnecessary for film formation is suppressed . The embodiment described above has the following advantages.・ Electron energy in plasma
It becomes possible to control the density, and by selecting the optimum parameters, it is possible to selectively increase the radicals required for film formation, and it is possible to form a high-quality film.・ High-quality radical formation density is high, which enables high-speed deposition of high-quality films. The generation of the high-density plasma reduces the width of the sheath formed above the substrate, and the energy of the ions accelerated in this sheath region decreases, so that damage to the film due to the ions can be prevented.・ High frequency power
The only pulsed applied, such as for discharge starts from part of the electrode, although stable plasma generation can not be ^{expected, 1 × 10 -3 ~5 × 10} -3 seconds ahead pulsed application of the RF power < By introducing the microwave pulse that has been carried out, a stable desired plasma state can be obtained instantaneously, and radical control becomes easier. Dust, the occurrence of Pa Tikuru is suppressed, occurrence of film missing is reduced, also improved maintainability of the apparatus. -Because of the high plasma generation rate, it is possible to form films at lower temperatures.

Next, a concrete example of forming an amorphous silicon (a-Si) film on a glass substrate using the apparatus shown in FIG. 1 and silicon nitride on the glass substrate using the same apparatus.
A specific example of forming a (SiNx) film will be described. Substrate size: 100 mm square Cathode size: 300 mm square Substrate-cathode distance: 50 mm High frequency power frequency : 13.56 MHz Microwave frequency : 2.45 GHz High frequency on time t1: 3 × 10 ⁻³ seconds High frequency off time t2: 5 × 10 ^-3 seconds Microwave on time t3: 5 × 10 ^-3 seconds Microwave off time t4: 3 × 10 ^-3 seconds High frequency application delay time t5: 1 × 10 ^-3 seconds a) a-Si film formation SiH ₄ flow rate: 50 sccm H ₂ flow rate: 250 sccm Film forming gas pressure: 1 × 10 ⁻¹ Torr Substrate temperature: 250 ° C. High frequency power: 200 W Microwave output: 150 W [Result] Film forming speed: 25 nm / min Particle density: 30 particles / 100 mm square ( Particle size 0.3
Optical band gap: 1.8 to 1.9 eV b) SiNx film formation SiH ₄ flow rate: 50 sccm NH ₃ flow rate: 150 sccm Film formation gas pressure: 1 × 10 ⁻¹ Torr Substrate temperature: 350 ° C. High frequency output: 500 W Microwave output: 150 W [Result] Deposition rate: 50 nm / min Particle density: 30 particles / 100 mm square (particle size 0.3
Optical band gap: 4.8 to 5.0 eV As described above, good results were obtained for both.

[0022]

According to the present invention, there is provided a plasma CVD method and apparatus in which a source gas introduced between a cathode electrode and a ground electrode in a film forming chamber is turned into plasma and the substrate is exposed to the plasma to form a thin film on the substrate. Therefore, the high-frequency power to the cathode electrode is turned on and off by turning the source gas into plasma.
Microwave to the film formation chamber with pulsed application by return
By applying a pulsed voltage by repeating the on and off of
And, the microwave application is synchronized with the high frequency power application.
By doing so, it is possible to control the generation of radicals and selectively generate and increase the radicals necessary for film formation, while suppressing the generation of radicals unnecessary for film formation, thereby suppressing the generation of dust and particles. High quality thin film at high speed while suppressing
It is possible to provide a plasma CVD method and apparatus that can be stably formed.

Moreover, regarding the timing of the application start <br/> microwave and high-frequency power, high frequency power sign microwaves applied
When it is preceded by the addition , more stable and stable plasma can be obtained, and accordingly, a good quality film can be formed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a schematic configuration diagram of another apparatus example for carrying out the method of the present invention.

FIG. 3 is a schematic configuration diagram of still another example of a device for carrying out the method of the present invention.

FIG. 4 is a graph showing the relationship between electron energy / density relative ratio, good quality radical density relative ratio, and plasma energy application.

FIG. 5 is a diagram showing a schematic configuration of a conventional plasma CVD apparatus.
It is.

[Explanation of symbols]

 1 Film-forming chamber 2 Cathode electrode 3 Ground electrode 4 High frequency pulse generator 41 High frequency pulse signal generator 42 Power amplifier 43 High frequency matching box 5 Heater 6 Exhaust system 7 Raw material gas supply device 8 Microwave pulse generator 81 Microwave pulse signal Generator 82 Microwave transmission source 83 Isolator 84 Matching device 85 Waveguide 851 Ceramics member 80 Phase synchronization circuit 86 Coaxial cable 87 Antenna 88 Quartz reaction tube 881 Microwave reflector 89 Valve 9 Substrate

Claims (4)

[Claims] 1. A plasma CVD method in which a source gas introduced between a cathode electrode and a ground electrode in a film forming chamber is turned into a plasma, and a substrate is exposed to the plasma to form a thin film on the substrate . The cathode
Pulsed application of high-frequency power on and off repeatedly to the pole
And repeat microwave on / off to the film forming chamber.
Pulsed application and the microwave application
A plasma CVD method characterized by being performed in synchronism with application of high-frequency power . 2. The on-time t1 for each application of high-frequency power is 1 ×
10 ⁻³ seconds ≦ t1 ≦ 10 × 10 ⁻³ seconds, each application of high frequency power
OFF time t2 is 1 × 10 ⁻³ sec ≦ t2 ≦ 10 × 10 ⁻³ sec,
Each microwave application ON time t3 is 2 × 10 ⁻³ seconds ≦ t3
≤15 × 10 ^-3 seconds, each microwave application off time t4
The plasma CVD method according to claim 1, wherein 1 × 10 ⁻³ seconds ≦ t4 ≦ 10 × 10 ⁻³ seconds . 3. The timing of the application start <br/> of the microwave and high frequency power, the high-frequency electrostatic the microwave
The plasma CVD method according to claim 2, wherein the application is started prior to the force , and the application start delay time of the high frequency power is set to 1 × 10 ⁻³ seconds or more and 5 × 10 ⁻³ seconds or less . 4. A plasma CVD apparatus for converting a source gas introduced between a cathode electrode and a ground electrode in a film forming chamber into plasma, exposing the substrate to the plasma to form a thin film on the substrate, and converting the source gas into plasma. In order to apply a high-frequency power to the cathode electrode in a pulse shape by repeatedly turning on and off , a microwave is turned on in the film forming chamber.
Means for applying a pulsed-Repeat off, said Ma
A method to synchronize the application of the microwave with the application of the high frequency power.
Plasma CVD apparatus characterized by comprising a stage.